1. Field of the Invention
The present invention generally relates to a combination weighing device. More specifically, the present invention relates to a combination weighing device that weighs articles with a plurality of weighing devices, and weighs articles in a predetermined target weight based upon these weight results.
2. Background Information
Amongst those weighing devices employed in a wide variety of applications, there are combination weighing devices that are employed to combine articles that do not have fixed and uniform weights, such as agricultural products, marine products, snack foods, or the like, into a combination that has a predetermined target weight. In this combination weighing device, articles are respectively distributed and supplied to weighing hoppers in order to measure the weights thereof, and a combination calculation is performed based upon these weight values. Then, a combination is selected that has a weight that matches the target weight or a weight the nearest to the target weight within a predetermined allowable range, and the articles are discharged from only the weighing hoppers in this selected combination.
In these types of combination weighing devices, there are those which are designed to increase the probability that the weight of a combination will fall within an allowable range with respect to the target weight and thus improve operational efficiency. For example, a combination weighing device in which the pool hoppers thereof also possess a weighing function has been proposed (e.g., see Japanese Published Patent Application No. S63-250528, pp. 2–3).
According to this device, both the weight values of articles in the weighing hoppers and the weight values of articles in the pool hoppers participate in the combination calculation, and thus the number of participating weight values during the combination calculation will reliably increase. Thus, there is a high probability that combinations will be completed.
In addition, a combination weighing device has been proposed in which the pool hoppers thereof possess a weighing function, and which supply articles to the weighing hoppers after the articles supplied from feeders (supply troughs) to the pool hoppers are measured into approximately predetermined weights by the pool hoppers (e.g., see Japanese Published Utility Model No. H02-655, pp. 1–3).
According to this device, an oversupply of articles to the weighing hoppers will be prevented when very small quantities of articles are supplied with vibrating feeders, and thus there is a high probability that combinations will be completed. In other words, in a combination weighing device that includes, for example, 10–12 weighing hoppers, a supply target value of articles to be supplied to each weighing hopper is set so that a combination will normally be complete with the weight values of 3,4 weighing hoppers. Thus, according to this combination weighing device, the weight of the articles supplied to the weighing hoppers will be close to the supply target value, and thus there is a high probability that combinations will be completed.
In addition, a combination weighing device has been proposed that controls the drives of the feeders (feeder drives) based upon a comparison between the weight values of the articles in the weight hoppers and the supply target value of the articles supplied to the weighing hoppers (e.g., see Japanese Published Patent Application No. H07-63599, pp. 3–5).
According to this device, articles with weights that are close to the supply target value are supplied to each weighing hopper, and thus there is a high probability that combinations will be completed for the reasons noted above.
Furthermore, there are devices which are designed to increase the probability that the weight of a combination will fall within an allowable range with respect to the target weight and thus improve operational efficiency. For example, a combination weighing device has been proposed in which articles from the weighing hoppers may be discharged in two directions—toward booster hoppers (auxiliary hoppers) and toward a collection chute (e.g., see Japanese Published Patent Application No. H07-63599, p. 6 and FIG. 5).
According to this device, both the weight values of articles in the weighing hoppers and the weight values of articles in the booster hoppers participate in the combination calculation, and thus there is a high probability that combinations will be completed because the number of weight values that participate in the combination calculation will reliably increase.
When a combination is not complete, these types of combination weighing devices supply additional articles from the pool hoppers to the weighing hoppers, and then perform a combination calculation again.
If these types of combination weighing devices are configured to supply additional articles to specific weighing hoppers, there is the possibility that an abnormality referred to as over-scale will occur if additional articles are repeatedly supplied thereto. Over-scale is an abnormal state caused when the weight of supplied articles exceeds a weight limit of the weighing hoppers or the volume of supplied articles exceeds the maximum allowed capacity of the weighing hoppers. If an over-scale state occurs, the combination weighing device will be compelled to cease operations, and thus operational efficiency will decline. in the combination weighing devices disclosed in the aforementioned
However, this problem are not addressed Japanese Published Patent Application No. S63-250528, Japanese Published Utility Model No. H02-655, or Japanese Published Patent Application No. H07-63599.
First, the combination weighing device disclosed in Japanese Published Utility Model No. H02-655 does not perform feedback control of the quantity of articles supplied from the feeders based upon the weight values of articles in the pool hoppers.
In addition, the combination weighing device disclosed in Japanese Published Patent Application No. H07-63599 determines the weight values of the first articles supplied to the weight hoppers. Thus, for example, in the event that feedback control is to be performed on the quantity of articles supplied by the feeders, it will be too late to do so if articles have already been supplied to the pool hoppers that supply articles from the feeders to the weighing hoppers in order to increase the speed of the process. The results of the feedback control will only be reflected in the next groups of articles supplied to the pool hoppers. This will create problems in the responsiveness and convergence of the control.
In addition, even though the combination weighing devices disclosed in Japanese Published Patent Application Nos. H07-63599 and S63-250528 will complete combinations with a high probability, these devices will not supply additional articles in situations in which a combination is finished in an incomplete state. With respect to the steps to be taken when a combination is incomplete, Japanese Published Patent Application No. H07-63599 discloses only that “all of the articles in the weighing hoppers will be discharged out of the system via the collection chute”, and thus one can only conclude that the aforementioned object of improving operational efficiency remains to be solved.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved combination weighing device that overcomes the above-discussed problems of the conventional combination weighing devices. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.